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But he'll be giving up day-to-day operational responsibility to Mark Fields, a chief architect of Ford's turnaround who has been the head of Ford's North and South American units. Fields has been promoted to the position of chief operating officer, effective on Dec. 1. Ford has not had a COO for several years.

Fields will now be "responsible for all business operations," Bill Ford said. That's a big deal, and a big change for the Blue Oval, which has been led by Mulally since 2006. Is this Ford's succession plan unfolding?

Officially, it's not quite a succession plan, but...It almost certainly is, though Bill Ford wouldn't come out and say so when asked. Clearly, the CEO job is Fields' to lose – but he'll get to do the operational part of it for a while first, with Mulally close at hand.

The good news is that Fields is almost certainly the best possible choice to succeed Mulally. Fields has been at Ford since 1989, and has served in several key international roles – including serving as Mazda's CEO and as Ford's Europe chief. He took over his current role as Ford's North and South America chief in 2005, and is credited with creating the initial version of Ford's turnaround plan.

While Fields was known for having something of an abrasive style earlier in his career, he appears to have moved past that. Bill Ford on Thursday praised Fields for having "grown" in his current role, saying that he felt that Fields had fully bought into Mulally's approach.

Fields will now be responsible for the day-to-day operation of Ford. "The really key message today is that Mark is going to take responsibility for leading the business plan reviews. I'm going to step back from that," Mulally told reporters.

That's a big deal. Ford's senior team meets every Thursday to hash out operational issues and discuss the progress of the company's plan. It's a meeting Mulally started and has run for years. Mulally will likely still attend, but Fields will be running those shows now.

That begs a big question for Ford shareholders: What will Mulally be doing?

Mulally takes a more strategic roleMulally's not going anywhere: He has promised Ford's board that he will stay on as president and CEO at least through 2014, he and Bill Ford both said on Thursday. But he said that he's planning to take more of a "strategic" focus.

What's that likely to mean? A few possibilities:

Long-range global expansion. Like its biggest rivals – General Motors (NYSE:GM), Volkswagen (NASDAQOTH:VLKAY), and Toyota (NYSE:TM) – Ford is aggressively expanding in emerging markets like China and Russia. Those markets continue to need focus, but Mulally may also begin work on getting Ford established in the next emerging markets, places like Malaysia and Indonesia, that are likely to start growing several years from now.

Long-term product development. Mulally has talked in the past about Ford's "technology roadmap," its work to develop leading solutions in everything from more advanced safety systems to alternatives to internal combustion engines. Mulally has often talked about Ford as a company that offers "personal transportation solutions," a deliberately chosen broad phrase. He'll get to spend more time and energy focusing on what Ford's products will be like a decade or more from now.

Leadership development. Mulally will obviously continue mentoring Fields as he grows into his new role. He's also likely to continue working with Ford's other senior leaders, and with folks like Bill Ford to identify and mentor other executive talent within the company.

The upshot: A bold – yet careful – move forwardToday's news was clearly intended to reassure investors: Analysts have been increasingly vocal about the uncertainty around Ford's transition plans. While the company stopped short of anointing Fields as its next CEO, today's actions – along with the reassurance that Mulally would be around for at least a couple more years – should largely address those concerns.

Mulally will now have more time and energy to engage with the longer-range issues that will drive the future of Ford for the next decade or more. This is critical work, and in a way it's similar to what Mulally did when he first arrived at Ford and set about implementing the company's turnaround plan.

As for Fields himself? He's a smart guy with the right experience who appears ready to lead Ford. We'll see how it goes.

Fool contributor John Rosevear owns shares of Ford and General Motors. Follow him on Twitter at @jrosevear. The Motley Fool owns shares of Ford. Motley Fool newsletter services have recommended buying shares of General Motors and Ford. Try any of our Foolish newsletter services free for 30 days.